Hydraulic device for the control of oil pressure pistons



United States Patent HYDRAULIC DEVICE FOR THE CONTROL OF OIL PRESSURE PISTONS 6 Claims, 2 Drawing Figs.

. 83/461 Int. Cl 826d 7/02 Field of Search 83/390,

[56] References Cited UNITED STATES PATENTS 2,323,710 6/ 1943 Hazelton s3/39ox 2,766,825 10/1956 Pater et al 83/390X Primary ExaminerAndrew R. J uhasz Assistant Examiner-James l1. Coan Atmmey- Lowry, Rinehart and Markva ABSTRACT: The invention provides a hydraulic device for the control of oil pressure pistons, especially for clamping down sheet metal plates to be cut with -a guillotine shear, wherein the generation of the effective oil pressure on the pistons is achieved by a plunger connected to the drive shaft of 33 4o :42 31 ,46 34 I t t I as 29 a5 36 Patented Oct. 6, 1970 Sheet Fig.2

Jnrenzor: WALTER 5cm Ursa HYDRAULIC DEVICE FOR THE CONTROL OF OIL PRESSURE PISTONS BACKGROUND OF THE INVENTION This invention relates to a hydraulic device for the control of oil pressure pistons, in particular for the clamping down of sheet metal plates about to be cut with a guillotine shear, whereby the generation of the effective oil pressure on the pistons is achieved through a plunger connected to the drive shaft of the guillotine shear. The plunger is contained in a cylinder whose area is divided into a high-pressure chamber and a low-pressure chamber connected by a pressure equalizing bore. This device will henceforth also be called an oil pressure generator.

When guillotining sheet metal plates these plates must be held fast on a table immediately before and during the cutting operation. Hydraulic oil pressure pistons are used for this purpose, the oil feed of which via a common oil pressure generator is controlled as a function of the movement of the shear. These oil pressure generators are so constructed that the pistons are already operative when the guillotine shear begins to cut and the pressure exerted on the pistons ceases immediately after the cutting operation ends. In this way the cut sheet metal plate does not hinder the upward stroke of the shear.

This was achieved with a known oil pressure generator, described in German Pat. No. 1.041 .766. by using a cam disc seated on the drive shaft of the oil pressure generator and the shear and working in conjunction with a pulley connected to the pistons. The use of a cam disc has considerable disadvantages since the cam disc is so highly stressed by the very high pressures occurring and because of its line contact with the pulley of the piston, that it has to be exchanged frequently due to wear. A further disadvantage is that the cam discs must have steep race portions so that the oil pressure can build up and drop suddenly. Such cam discs have a small transitional radius and are thus exposed to very high loads and considerable wear.

It is thus more advantageous to control the piston via a connecting rod with an eccentric disc since such a drive has a less surface pressure between the drive elements then the line contact ofa cam disc. The use of a connecting rod with an eccentric disc has not been possible before since with the known oil pressure generators it was impossible to achieve any noteworthy operation of the generators before the shear became operative, i.e. the oil pressure build-up was not very rapid. The top dead center position of the piston could not be advanced with respect to the top dead center position of the shear because this resulted in the oil pressure at the bottom dead center position of the eccentric disc of the oil pressure generator dropping too rapidly.

SUMMARY OF THE INVENTION It is the object of the present invention to provide a hydraulic device for the control of oil pressure pistons which permits the top dead center positions of the pistons to be advanced in relation to the movement of the shear so that a connecting rod with an eccentric disc can be used as a drive which is free from the disadvantages of the known cam disc drives.

To attain this object the present invention provides a hydraulic device for the control of oil pressure pistons, especially for clamping down sheet metal plates to be cut with a guillotine shear, wherein the generation of the effective oil pressure on the pistons is achieved by a plunger connected to the drive shaft of the guillotine shear and guided in a cylinder divided into a high-pressure chamber and a low-pressure chamber connected by a first pressure equalizing bore in the wall of the high-pressure chamber on a level higher than the level of the lower edge of the plunger in its bottom dead center position, so that the high pressure in the high-pressure chamber begins to decrease only after the intake stroke of the plunger has commenced.

With this arrangement the high pressure does not drop at the bottom dead center position of the plunger as soon as the same begins its upward movement, but only after the plunger has travelled a predetermined distance upwards to its top dead center position. It is thus possible to use an oil pressure generator whose plunger is nonpositively connected to the drive shaft via a connecting rod and an eccentric disc, the eccentric disc for the drive of the plunger being preferably advanced over the eccentric disc for the guillotine shear drive on a common drive shaft in the direction of rotation.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an oil pressure generator comprising a housing 1 forming an oil chamber 13 about two-thirds of which are filled with oil 2. The housing 1 contains a cylinder 3 in which a cup-shaped plunger 4 having a plunger chamber 12 is able to move up and down. The plunger 4 is connected by a gudgeon pin 5 to a connecting rod 6 located on an eccentric disc 7 carried by a drive shaft 8 arranged to rotate in the direction of the arrow 9.

A suction valve 10 is arranged in the head of the plunger 4 and serves to shut off a bore 11 in the plunger head during the compression stroke of the plunger 4. This bore 11 connects the plunger chamber 12 to the oil chamber 13.

An inner plunger 14 enclosing a high-pressure chamber 15 is inserted in the cylinder 3 and extends into the plunger chamber 12. The head of the inner plunger 14 has a bore 16 which is shut off by a nonreturn valve 17 during the intake stroke of the plunger 4.

A first radial pressure equalizing bore 18 extends through the middle portion ofthe wall of the inner plunger 14 and connects the high-pressure chamber 15 to an annular low-pressure chamber I9. A second radial pressure equalizing bore 20 is provided in the wall of the cylinder 3 on a level higher than that of the first pressure equalizing bore 18 and connects the annular low-pressure chamber 19 to the oil chamber 13 when the plunger 4 is in its top dead center position. The low-pressure chamber 19 is further connected to the oil chamber 13 by a bore 21 which is fitted with a suction valve 22. This suction valve 22 opens the bore 21 when the plunger 4 is on its intake stroke, i.e. moves upwardly. The low-pressure chamber 19 is also connected to the oil chamber 13 by a bore 23 in which a relief pressure valve 24 for adjusting the low pressure is accommodated. The relief pressure valve 24 has a plunger which is loaded by a spring 25 the tension of which can be adjusted by a set screw 26.

The high-pressure chamber 15 isconnected to the low-pressure chamber 19 by a channel 27 with a shutoff valve 28, and to the oil chamber 13 by a channel 29. A bypass 30 leads from this channel 29 into the oil chamber 13 and can be shut off by a combined relief pressure and storage valve 31 having its plunger kept under compression by a spring 32 the tension of which can be adjusted by means of a set screw 33.

A connecting channel 34 is connected to the housing 1 so as to communicate with the high-pressure chamber 15. The pres sure oil is fed through said connecting channel 34 to one or more cylinder and piston assemblies 35. Each cylinder and piston assembly 35 comprises a spring-loaded piston rod 36 which presses the sheet metal plate 37 down onto a table 38 I when a sheet metal plate is to be cut by the guillotine shear shown in FIG. 2.

It can be inferred from FIG. 2 that the cutter guide 39 together with its terminal strip 40 can be moved up and down by a second connecting rod 41. To achieve this end, the connecting rod 41 is pivotally connected at its free end by a pin 42 to one stanchion 43 of the cutter guide 39. The other end of the connecting rod 41 is seated on an eccentric disc 45 which is supported by the drive shaft 8. It can be seen from FIG. 2 that the connecting rod 6 and the eccentric disc 7 for the plunger 4 are arranged on the shaft 8 in positions advanced over the connecting rod 41 and the eccentric disc 45 for the drive of the cutter guide 39. it thus occurs that the plunger 4 has passed its bottom dead center position and is again on the upward stroke when the cutter guide 39 reaches its bottom dead center position.

The device shown in the drawings operates as follows:

As it moves down from its top dead center position, the plunger 4 shuts off first the second pressure equalizing bore and then forces oil through the first pressure equalizing bore 18 into the high-pressure chamber 15, out of the low-pressure chamber 19 through the shutoff valve 28 into the high-pressure chamber 15 and out of the plunger chamber 12 via the nonreturn valve 17 through the bore 16 into the high-pressure chamber 15, from which the oil flows out through the connecting channel 34 into the cylinder and piston assemblies 35. At this point the low-pressure chamber 19 is still directly connected to the highpressure chamber 15 by the first pressure equalizing bore 18. As soon as the piston rods 36 begin to press the sheet metal plate 37 onto the table 38, the pre-filling operation ends, i.e. the cylinder and piston assemblies can take no more of the oil forced in by the plunger 4. The excess pressure oil thus flows through the relief pressure valve 24 into the oil chamber 13. During further down strokes and during the progress of the pressure stroke, the first pressure equalizing bore 18 is shut off by the plunger 4. The oil forced out of the plunger chamber 12 through the nonreturn valve 17 can thus no longer escape from the high-pressure chamber 15 into the low-pressure chamber 19, since the shutoff valve 28 operating in this direction also shuts off the channel 27. The oil forced out of the plunger chamber 12 must therefore pass through the nonreturn valve 17 and through the high-pressure chamber 15 to the combined relief pressure and storage valve 31 which is adjusted for high pressure. This valve 31 opens when the set high-pressure level which can be adjusted by tensioning the compression spring 32 is reached, so that further excess oil can flow out through the bypass 30 into the oil chamber 13. First of all a stock volume of oil is collected in a storage chamber 46 since the plunger of the combined relief pressure and storage valve 31 only opens the bypass 30 when forced up in the storage chamber 46 by a certain amount from the channel 29, Le. by the distance H. The distance H and thus the size of the storage chamber 46 correspond to the distance of the upper mouth of the channel 29 from the underside of the bypass 30.

lfthe plunger 4 has reached its bottom dead center position, the oil in the high-pressure chamber 15 and in the connecting channel 34 will be held at high pressure at the subsequent start of the intake stroke and upward movement of the plunger 4 by the reservoir in the combined relief pressure and storage valve 31, since the nonreturn valve 17 and the shutoff valve 28 prevent back flow into the plunger chamber 12 or the lowpressure chamber 19. During this stage of the upward move ment of the plunger 4 the cutter guide 39 executes a downward movement as a result of the advanced position of the eccentric disc 7 in relation to the eccentric disc 45, so that the piston rods 35 hold the sheet metal plate 37 under tension on the table 38 although the plunger 4 is already moving upwardly.

If the plunger 4 opens the first pressure equalizing bore 18, the oil volume is relieved through the open relief pressure valve 24. At the same time the growing low-pressure chamber 19 is being filled with oil through the suction valve 22 and the growing plunger chamber 12 is being filled with oil through the open suction valve 10. As the plunger 4 continues its upward movement the second pressure equalizing bore 20 is opened so that complete drop in pressure and volume e ualization in all oil chambers and channels occurs.

he high pressure created by the Oll pressure generator thus does not fall off at the bottom dead center position of the eccentric disc 7 but later, i.e. after the plunger 4 has reached a point on its intake stroke high enough to open the first pressure equalizing bore 18.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

I claim:

1. A hydraulic device for the control of oil pressure pistons, especially for clamping down sheet metal plates to be cut with a guillotine shear, wherein the means for generating the effective oil pressure on the pistons comprises a drive shaft, a cylinder having a high-pressure chamber and a low-pressure chamber, a cup-shaped plunger in said cylinder and operatively connected to said drive shaft, an inner plunger in said cylinder separating said highand low-pressure chambers, and a pressure equalizing bore connecting said highand low-pressure chambers and located in the wall of said inner plunger at a position such that said plunger in its bottom dead center position blocks said bore whereby the high pressure in the high-pressure chamber begins to decrease only after the intake stroke of the plunger 15 has commenced.

2. A hydraulic device as claimed in claim 1 further comprising a nonreturn valve in said inner plunger.

3. A hydraulic device as claimed in claim 1 further comprising a fluid reservoir and a second pressure equalizing bore in the wall of said cylinder above said first mentioned pressure equalizing bore connecting said low-pressure chamber with said fluid reservoir.

4. A hydraulic device as claimed in claim 1 further comprising a storage valve and conduit means connecting said storage valve with said high-pressure chamber, said storage valve including means for accumulating fluid from said high-pressure chamber and for releasing said fluid above a predetermined pressure.

5. A hydraulic device as claimed in claim 1 further comprising means eccentrically connecting said plunger with said drive shaft and further means eccentrically connecting said guillotine shear with said drive shaft, the relative positions of said two eccentric connecting means on said drive shaft being such that said plunger is driven in advance of the guillotine shear.

6. A hydraulic device as claimed in claim 5 wherein the means connecting said plunger to said drive shaft and the means connecting said guillotine shear to said drive shaft each comprise an eccentric disc mounted on said drive shaft and a connecting rod connected to said eccentric disc. 

